Fuel metering system



1953 l. H. EDELFELT ET AL FUEL' METERING SYSTEM Filed March 17, 1948 yam2d /7 Inventors 1 Ivan H. EdelfePo; Donald E. G am by A Their Att ovney.

Patented Feb. 10, 1953 FUEL METERING SYSTEM Ivan H. Edelfelt and DonaldE. (iarr, Schenectady, N. Y., assignors to General Electric Company, acorporation of New York Application March 17, 1948, Serial Iva/15,414

Claims.

Our. invention relates to a fuel metering system and more particularlyto a fuel metering system of th type utilized to supply a controlledamount of fuel to a reaction motor carried on the tip of a helicopterrotor blade.

In supplying fuel to a reaction motor located at the tip of a rotatingblade, a problem arises in that the fuel that is carried .in thefuelline running from the hub of the rotor to the tip of the rotor bladedoes not flow evenly because after the fuel has proceeded a shortdistance through the fuel line, the centrifugal force on the fuel isgreat enough to cause it to break away from the rest of the fuel column.This causes intermittent fuel feeding to the combustion chamber andresult in too much fuel one instant and too little, or none, the nextinstant. Since in this fuel metering system a fuel pressure operatedcontrol valve is located adjacent thereaction motor, a further problemarises in that during operation large pressure due to centrifugal force,in addition to the fuel pump pressure, is being impressed upon thevalve. It is pointed out that quite often the pressure due tocentrifugal force is much greater than that supplied by the fuel pumpand yet it isnecessary that the fuel pressure operated control valve beonly responsive to fuel pump pressure. 7

Thus, one of the objects of this invention is to provide some fuelmetering system to eliminate the fuel surging and breaking away of fuelin the fuel line due to centrifugal force and to eliminate the effectsof such surging upon the feed of fuel to the combustion chamber.

Another object of .the invention is to provide a fuelmetering systemvalve which is solely responsive tothe fuel pump p'ressurereg'ardless ofwhat the centrifugal forceis, even though the pressure due to thecentrifugal force is much greater than the fuel pump pressure.

Further objects and advantages .of our invention will become apparent asthe following description. proceeds and the features ofnovelty whichcharacterize our invention willbe pointed out with particularity in theclaims annexed to and forming a part of this specification.

In the drawing,

Fig. 1 shows a reactionmotor powered helicopter rotor having a fuelmetering system embodying our invention.

Fig. 2 is a cross sectional view showing conv structional details.of.the. fuel metering valve shown diagrammatically in Fig. 1. V I

' Fig. 3 .shows a modification of the structure shown in Fig. 2.

' Referring to Fig. 1 Of theorem-mg. We have fill-39.35)

shown diagrammatically ajetpowered helicopter rotor comprising allftingibladeextending from av hub 2 and carrying adjacentits outer'tip,

reaction motor 3. Mounted substantially concentrically 'withthegcenterof. rotation-of the rotor assembly is a fuel pump 4, whose output iscontrolled by a suitable control 5. whichis operated by thepilot. Thefuelpump 4. is. manifolded to fuel supply lines 6 anddeliversfuel atvarying pressures. The fuelsupply line. 6 is carried within the.liftingblade l and runs. the length of said blade towards the tip. tofuel .valve 1 which, is mounted adjacent the reaction motor 3substantially in the position indicated. Connected to the outlet of thefuel valve 1 is afuel conduit 8 leading to the combustion chamberofreaction motor 3. I

Referring to Fig. 2 of. the. drawing. whlch is a cross sectional view offuelvalve, 'lshownyin Fig. 1, we have shown the valve as comprisingavalve barrel 9 and a valve barrel extension Sta.- Lying withinthe-valve barrel 9 and-itsextension 9a is a weighted valving' piececonsisting of a fuel. flow governing piece In which. cooperatesin actionwith mass IZ-through rod ll. In Fig. 2, rod H is shown threaded tomass-l2. Due to possible difficulty in aligning parts l0 and, analternative construction shown inFig. 3 is suggested. Here rod Ila,corresponding to rod ll of Fig.2, fits loosely in shaft 25 in part l2a,corresponding to part l2. The bottom of shaft or recess 25, as well asthe correspondingendbf rod ,l-la, are spherically shaped to provide abearing surface. Rod I la coopearting-with part 12 aligns parts l0 and.lZa. .It is pointed out that rod may. be part of piece In turned down,to size or a construction similar to that described above may be usedto'align parts 10 and -l l. ,;Mas s-l2 is selected of such size. thatthetotal-massof the valvingpiece is in accordance with the theorysetforth .in another section ofthis specification. Also lying within thevalve barrelextension 9a is a spring l3 which cooperates with thevalving piece through themasslllto bias the ffuelflfiow governin pieceI0 so that no fuel flow result's. It is important that atno time-shouldvalvi'ng piece In butt up against fuelinlet. orifice. l4 so as toprevent. the fuel pressure due to'centrifugal force from being exertedin chamber. 1'5. f To insure this, nipple IB. mounted 'on-valving piecein has in its head a groo'vej'o'r grooves l'lf'orcoinmunicating thefuelto. chamberlli incasenipple I6 is butted up against fuelinlet 14.3spring-1.3 is also in contact with a back'p'lat'e l8 the position ofwhich may be radiallyadjusted, as back plate I8 is threaded-to cooperatewith threads in member 15. By adjusting the back plate l8, the restoringforce in spring 13 may be varied.

The fuel flow governing piece I8 has in its surface a helically arrangedpassageway or groove 20 of variable cross sectional area which in thenormal position does not pass fuel, but which when in alignment with aninternal circumferential recess 2! connected to valve outlet 22, doespass fuel. The valve barrel 9 has a slot 23 for draining any fluid thatseeps past member if) and a shoulder 24 that acts as a limit stop formovement of member l0. Shoulder 24 also acts to catch and direct to slot23 any fuel that seeps past member Ill and is thrown out along the walldue to centrifugal force.

In operation, the fuel pump, 4 provides the amount of fuel required atpressure, which pressure is impressed upon the fuel all along the fuelline to the valve I where the fuel pump pressure operates the valvewhich opens to -permit fuel flow; .When 'the rotor is rotating thefue1Lin the fuel line is also being rotated about the center of rotationan'clnow the fuel in the fuel line is subjected to anadditional'pressure caused by the centrifugal forces of the fuel itself;The pressure due to this force increases as one moves toward the tip ofthe'rotor blade and reaches a maximum at the tip of said blade. Thus atany point in the fuel line the pressure is equal to the sum or thepressures caused b'y centrifugal force plus that supplied by the fuelpump. It is desirable, however;- that the fuel valve respond only to thefuel pump pressure. To accomplish this object, the valvingpiecein theValve is built of such mass that itscentrifugal force is equal to thecentrifugal force of the column of fuel in the fuel-line. Then, sincethe fuel valve is unresponsive to centrifugal force, the fuel line iseffectively closed at the tip and the object of eliminating surging andbreak away of fuel in the fuel line is accomplished because the fuelline'is filled at all times. In operation, theonly unbalanced force isthat supplied by the fuel pump pressure and when that is applied thevalving piece moves against the spring untila position is reached wherethe spring pressure equals the fuel pump pressure which is adjustablefor control purposes. The passageway 20 then in communication withrecess 2| and fuel flows, and now the fuel is volumetrically metered bythe cross sectional area of said passageway; The cross sectional area ofpassageway 20 is so designed that it permits-the correct volumetric flowto pass as the fuel pump pressureisvaried and the valving piececompr'esses "the spring a proportional amount, Thus member-1B is solelyresponsive to fuel pump pressure and acts as a pressure regulated fuelmetering device.-

The theory upon which the valving piece design is founded is as follows:Assume the rotor blade is rotating at some speed w. Call the length ofthe column of fluid from the center of rotation to the valve inlet Z andlet T be the distance from the center of rotation of the rotor to'thecentroid of the valving piece. Further assume that 1'=Z, that is thecentroid of the valving piece coincides with the center line of thevalve fuel inlet. (This latter assumption is solely for simplicity ofderivation.) Also, let the mass of the fluid be pr/fOOt and themass ofthe valving piece be pv. Then, for any given to, the force exerted bythe column of fluid at the valve inlet is 4 But prZ=the total weight ofthe fluid in the fuel line, and

is the centroid of the fuel line. Now, the force that the valving piecewill exert on the fluid is, for the same no,

In order that the two forces be equal we have ma :(p foot-ly- Or,expressed in words, the mass of the valving piece times the distance ofits centroid from the center of rotation must equal the mass of thefluid column times the distance of its centroid from the center ofrotation.

Since for any given design or configuration, of fuel system, thevariables, 1, pi, and r, are readily determinable, it becomes possibleto calculate what the mass of the valving piece should be. Obviously thevalving piece may be so constructed that itstotal mass may beconveniently varied so as to be easily adaptable to a variety of fuelsystem configurations.

It will be readily apparent to one skilled in the art that the valvingpiece described can alternately be broken into equivalent cooperatingcomponents comprising a radially movable spe cific mass actuatingthrough some means, such as a bell crank, lever, wire, spring, etc., afuel porting system in combination with a fuel metering means, such as ashaped needle valve and port, a gate valve, a sleeve valv or othervalving means suitable for metering fluid volumetrically.

Thus, while we have illustrated and described a particular embodiment ofour invention, modi fications thereof will occur to those skilled in theart. We desire it to be understood, therefore, that our invention is notto be limited to the particular arrangement disclosed, and we intend inthe appended claims to cover all modifications which do not depart fromthe spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A fuel metering system for a reaction motor mounted on a rotorpowered thereby comprising a fuel pump having an adjustable outputpressure, a fuel line interconnecting said motor and said pump, saidfuel line extending radially outward along said-rotor so that due torotation of said rotor the fuel pressure therein is affected by both thefuel pump pressure and the centrifugal force acting on the fuel therein,a fuel pressure responsive control valve interposed in said fuel lineadjacent said motor for metering fuel thereto, said control valve havinginlet and outlet con-' nections, a valving piece for regulating the flowbetween the said connections, said valving piece being radially movableand having a predetermined massof such magnitude that when the rotor isin operation, the centrifugal force of said valving piece is equal andopposite to the centrifugal force of the fuel column, a radially movablemeans cooperating with said valving piece to bias it in a closingdirection, and means responsive to the fuel pump pressure for actuatingsaid valving, Piece in an opening direction.

2. A fuel metering system for a reaction motor mounted on a rotorpowered thereby comprising a fuel pump having an adjustable outputpressure, a fuel line interconnecting said motor and said pump, saidfuel line extending radially out- Ward along said rotor so that due torotation of said rotor the fuel pressure therein is affected by both thefuel pump pressure and the centrifugal force acting on the fuel therein,a fuel pressure responsive control valve containing a valving pieceinterposed in said fuel line adjacent said motor for metering fuelthereto, said valving piece being radially movable and having apredetermined mass of such magnitude that when rotor is in operation,the centrifugal force of said valving piece is equal and opposite to thecentrifugal force of the fuel column, and means responsive to the fuelpump pressure for metering the fuel flow.

3. In a fuel metering system for a reaction motor, said system beingsubjected to centrifugal force, a fuel pump, a fuel line connecting saidfuel pump and said reaction motor, and a control valve located in saidfuel line adjacent said motor, said control valve containing a radiallymovable valving piece responsive to centrifugal force to reduce the flowof fuel, the centrifugal force acting upon said fuel opposing the motionof said valve whereby the effect of centrifugal force on the rate offuel flow is nullified.

4. A fuel metering system for a, reaction motor mounted on a rotorpowered thereby comprising a fuel pump having an adjustable outputpressure, a fuel line interconnecting said motor and said pump, saidfuel line extending radially outward along said rotor so that due torotation of said rotor and fuel pressure therein is affected by both thefuel pump pressure and the centrifugal force acting on the fuel therein,a fuel control valve interposed in said fuel line adjacent said motorfor metering fuel thereto, said fuel control valve containing a radiallymovable predetermined mass of such magnitude and so positioned withrespect to the incoming fuel that said predetermined mass impresses uponsaid incoming fuel a force equal and opposite to the centrifugal forceof the fuel itself, said fuel control valve containing a valving piececooperating with said movable predetermined mass, means for biasing thevalving piece to normally restrict flow, and means for volumetricallymetering the fuel flow.

5. A fuel metering system for a reaction motor mounted on a rotorpowered thereby comprising a fuel pump having an adjustable outputpressure, a fuel line interconnecting said motor and said pump, saidfuel line extending radially outward along said rotor so that due torotation of said rotor the fuel pressure therein is affected by both thefuel pump pressure and. the centrifugal force acting on the fueltherein, a fuel pressure responsive control valve interposed in saidfuel line adjacent said motor for metering fuel thereto, said controlvalve having inlet and outlet connections, a valving piece forregulating the volumetric fiow between the said connections, said valvecontaining a radially movable predetermined mass of such magnitude andso positioned that said predetermined mass impresses upon the fuelentering the valve a force equal and opposite to the centrifugal forceof the fuel itself, and means responsive to the fuel pump pressure foractuating said valving piece in an opening direction.

IVAN H. EDELFELT. DONALD E. GARR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,021,521 Hroult Mar. 26, 19121,699,676 Rush Jan. 22, 1929 2,446,523 Bradbury et a1 Aug. 10, 19482,509,359 Margolis May 30, 1950

